JP2006017747A - Method for producing polarizer, polarizer, polarizing plate, optical film, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polarizer with which metal ions can be efficiently contained in a polarizer composed of a polyvinyl alcohol film. <P>SOLUTION: In the method for producing the polarizer is disclosed wherein the polyvinyl alcohol film is at least subjected to a dyeing step using a dichroic dye, a uniaxial stretching step and a metal ion processing step, and then subjected to a water washing step and a drying step, a metal sulfate salt is used in the metal ion processing process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a polarizer. Moreover, this invention relates to the polarizer obtained by the said manufacturing method, the polarizing plate using a polarizer, and an optical film. Further, the present invention relates to an image display device such as a polarizing plate, a liquid crystal display device using an optical film, an organic EL display device, and a PDP.

  Conventionally, as a polarizer used in a liquid crystal display device or the like, a polyvinyl alcohol film dyed and stretched with a dichroic dye such as iodine has been used because it has both high transmittance and degree of polarization. Moreover, the said polarizer is normally used as a polarizing plate by which protective films, such as a triacetyl cellulose film, were bonded to the single side | surface or both surfaces.

  In recent years, liquid crystal display devices are often used for a long time under high temperature conditions or the like due to their wide use, and liquid crystal display devices with little change in hue according to the intended use are demanded. Accordingly, the polarizing plate is also required to have durability that does not deteriorate the optical characteristics when left under high temperature conditions or when left under high temperature and humidity conditions. For example, it is shown that color tone adjustment and durability can be improved by adding a metal ion such as cobalt, nickel, zinc, etc., to a polarizer made of a polyvinyl alcohol film dyed with iodine (for example, Patent Document 1, (See Patent Document 2 and Patent Document 3).

  Introduction | transduction of the said metal ion in a polyvinyl alcohol-type film is performed by immersing a polyvinyl alcohol-type film in the aqueous solution containing the said metal ion, for example. After the metal ion treatment, a drying process is performed. However, when the polyvinyl alcohol film is dried, a metal salt is deposited on the dried film surface, resulting in an appearance defect. Therefore, before the drying step, a cleaning step such as immersing the film in pure water is provided.

However, if a washing process is performed, metal ions contained in the polyvinyl alcohol film will flow out of the film. As a result, it has been difficult to stably add an amount necessary for color tone adjustment and heat resistance to the polarizer.
JP 54-16575 A Japanese Patent Laid-Open No. 61-175602 JP 2000-35512 A

  An object of this invention is to provide the manufacturing method of a polarizer which can make a polarizer which consists of a polyvinyl alcohol-type film contain a metal ion efficiently.

  Another object of the present invention is to provide a polarizer obtained by the production method, a polarizing plate using the polarizer, and an optical film. Furthermore, it aims at providing the image display apparatus using the said polarizing plate and an optical film.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by the following polarizer and production method thereof, and have completed the present invention.

That is, the present invention provides a polarizer comprising a step of subjecting a polyvinyl alcohol film to at least a dyeing treatment step with a dichroic dye, a uniaxial stretching treatment step, and a metal ion treatment step, followed by a water washing step and then a drying step. In the manufacturing method,
The present invention relates to a method for producing a polarizer, wherein a metal sulfate is used in a metal ion treatment step.

  In the production method of the present invention, when a polyvinyl alcohol film dyed with a dichroic dye is subjected to a metal ion treatment, a metal sulfate is used as a compound that releases metal ions. The amount of swelling is reduced. As a result, the amount of metal ions flowing out of the film can be reduced even when the film containing metal ions is washed with water, and the film contains the necessary amount of metal ions after washing with water. Can be made. In addition, the film treated with metal ions using a metal sulfate salt has a small amount of metal ions flowing out from the film, so that it is easy to keep the metal ions in the washing bath used for water washing at a low concentration. Contamination of the film surface can be prevented.

  As described above, according to the production method of the present invention, the retention rate of metal ions contained in a polyvinyl alcohol film by metal ion treatment before and after water washing can be increased. The retention rate (% by weight) is the ratio of the weight of metal ions contained in the polyvinyl alcohol film before and after water washing, (weight of metal ions contained in the polyvinyl alcohol film after water washing) / (before water washing). It is a value represented by the weight of metal ions contained in the polyvinyl alcohol film. Although the said retention rate changes with other conditions, such as a kind of metal sulfate, it is 80 to 90% of range normally, and can contain a metal ion efficiently in a polyvinyl alcohol-type film.

  In the method for producing the polarizer, a polyvinyl alcohol film is subjected to at least a dyeing treatment step with a dichroic dye, a uniaxial stretching treatment step, a metal ion treatment step and a boric acid treatment step, followed by a water washing step and then a drying step. It is preferable to apply.

  In the method for producing the polarizer, it is preferable that the polyvinyl alcohol film is subjected to a dyeing process with a dichroic dye and then subjected to a uniaxial stretching process, a metal ion treatment process, and a boric acid treatment process at the same time.

  Moreover, this invention relates to the polarizer obtained by the said manufacturing method. The polarizer of the present invention is characterized by containing a sulfur atom. In the polarizer of the present invention obtained by the above production method, a metal sulfate salt is used for metal ion treatment, and the metal sulfate is introduced into the polarizer in an ionic state. Therefore, the polarizer obtained by the production method of the present invention can be confirmed by whether or not it contains a sulfur atom. Usually, the sulfur atom content of the polarizer obtained by the present invention is about 0.01 to 0.6% by weight.

  The present invention also relates to a polarizing plate in which a transparent protective layer is provided on at least one surface of the polarizer. The present invention also relates to an optical film in which at least one polarizing plate is laminated. Furthermore, this invention relates to the image display apparatus characterized by using the said polarizing plate or the said optical film.

  Polyvinyl alcohol or a derivative thereof is used as a material for the polyvinyl alcohol film applied to the polarizer of the present invention. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. can give. Polyvinyl alcohol having a polymerization degree of about 1000 to 10000 and a saponification degree of about 80 to 100 mol% is generally used.

  The polyvinyl alcohol film may contain an additive such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol film.

  The polyvinyl alcohol film is subjected to a dyeing process, a uniaxial stretching process, and a metal ion treatment process with a dichroic dye according to a conventional method. Further, boric acid treatment can be performed after the dyeing treatment step.

  The dyeing process is performed by adsorbing or orienting iodine or a dichroic dye on the film. The dyeing treatment is generally performed by immersing the film in a dyeing solution. As the staining solution, an iodine solution is generally used. As the iodine aqueous solution used as the iodine solution, in addition to iodine, an aqueous solution containing iodine ions with potassium iodide or the like is used as a solubilizing agent. The iodine concentration is about 0.01 to 0.5% by weight, preferably 0.02 to 0.4% by weight, and the potassium iodide concentration is about 0.01 to 10% by weight, and further 0.02 to 8% by weight. % Is preferably used.

  In the iodine dyeing treatment, the temperature of the iodine solution is usually about 20 to 50 ° C, preferably 25 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds.

  If necessary, the polyvinyl alcohol film may be immersed in water and washed before the dyeing treatment. By washing the polyvinyl alcohol film with water, it is possible to clean the surface of the polyvinyl alcohol film and anti-blocking agents, and also to prevent unevenness such as uneven dyeing by swelling the polyvinyl alcohol film. There is also.

  The stretching method in the uniaxial stretching treatment is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. Examples of the stretching means of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. Stretching can also be performed in multiple stages. In the stretching means, the unstretched film is usually heated. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The stretch ratio of the stretched film can be appropriately set according to the purpose, but the total stretch ratio is about 2 to 7 times, preferably 3 to 6.5 times, and more preferably 3.5 to 6 times. The thickness of the stretched film is preferably about 5 to 40 μm.

  The uniaxial stretching process may be performed at any stage before the dyeing process, during the dyeing process, or after the dyeing process. In addition, the uniaxial stretching treatment can be performed in a plurality of steps, and for example, it can be performed in two or three stages before the dyeing process, at the time of the dyeing process, and after the dyeing process.

  The metal ion treatment is performed by immersing the polyvinyl alcohol film in an aqueous solution containing a metal sulfate salt. Various metal ions are contained in the polyvinyl alcohol film by metal ion treatment.

  As metal ions, metal ions of transition metals such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, and iron are particularly preferably used in terms of color tone adjustment and durability. Among these metal ions, zinc ions are preferable from the viewpoints of color tone adjustment and heat resistance. That is, as the metal sulfate salt, cobalt sulfate, nickel sulfate, and zinc sulfate are preferably used.

  When metal sulfate is used for metal ion treatment, the retention rate of the metal ions contained in the polyvinyl alcohol film is high depending on the type of metal salt. This is because the amount of the metal salt contained in the polyvinyl alcohol film is related. That is, when a metal sulfate salt is used, since the polyvinyl alcohol film swells little, the metal ions contained in the polyvinyl alcohol film are small, but the amount of metal ions flowing out during washing with water is small. It is considered that the retention rate of metal ions is high. On the other hand, when other metal inorganic salts are used, it is considered that the polyvinyl alcohol-based film is greatly swelled and metal ions easily enter and exit before and after washing with water, and as a result, the metal ion retention rate is lowered.

This difference in the degree of swelling is also correlated with the salting-out power of the anion. In a surface inert solution to which metal salts are added, the magnitude of the surface tension depends on the type of salt of the metal salt. In general, it is known from the Hofmeister permutation that the magnitude of the salting-out power of anions for the same metal salt is citric acid> tartaric acid> SO ₄ > CH ₃ COO>Cl>Br> NO ₃ >I> SCN. It has been. Since sulfate has a large salting-out power, it is considered that swelling of the polyvinyl alcohol film is reduced by increasing the surface tension of the aqueous solution, and metal ions in the polyvinyl alcohol film are prevented from flowing out.

  The concentration of the metal sulfate in the aqueous solution containing the metal sulfate varies depending on the type of metal ion, but is about 1 to 20% by weight, preferably 5 to 15% by weight, and more preferably 5 to 10% by weight. When the concentration of the metal sulfate salt is less than 1% by weight, it is difficult to sufficiently contain the metal ion amount necessary for obtaining properties such as durability in the polyvinyl alcohol film. On the other hand, if it exceeds 20% by weight, the swelling of the polyvinyl alcohol film is reduced, and the amount of metal ions contained in the polyvinyl alcohol film is reduced.

  In addition to the metal sulfate, examples of the metal salt include inorganic acid salts such as hydrochloride, nitrate, acetate, and iodide, and organic acid salts such as citrate, tartrate, and acetate. These metal salts (other than the metal sulfate salts) can be mixed with the metal sulfate salts and used as long as the object of the present invention is not impaired. As these metal salts, organic acid salts having high salting-out power are preferable.

  In the metal ion treatment, the temperature of the aqueous solution containing a metal sulfate salt is usually about 15 to 70 ° C, preferably 25 to 67 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds.

  The stage of the metal ion treatment is not particularly limited, and may be before the iodine staining treatment or after the iodine staining treatment. Alternatively, the metal salt may be present in the dyeing solution and may be performed simultaneously with the dyeing treatment. Moreover, it can carry out simultaneously with a uniaxial stretching process. In the production method of the present invention, it is preferable to perform metal ion treatment simultaneously with the uniaxial stretching treatment step after the dyeing treatment.

  The boric acid treatment is performed by immersing a polyvinyl alcohol film in an aqueous boric acid solution. The boric acid concentration in the boric acid aqueous solution is about 2 to 15% by weight, preferably 3 to 10% by weight. In the boric acid treatment, the temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C. The immersion time is usually about 1 to 1200 seconds, preferably about 10 to 600 seconds, and more preferably about 20 to 500 seconds.

  The step of performing the boric acid treatment is after the iodine staining treatment. The boric acid treatment is performed during or after uniaxial stretching. In the production method of the present invention, boric acid treatment is preferably performed simultaneously with the uniaxial stretching treatment step after the dyeing treatment.

  The treated polyvinyl alcohol film (stretched film) is subjected to a water washing step and a drying step according to a conventional method.

  The water washing step is usually performed by immersing a polyvinyl alcohol film in pure water. The water washing temperature is usually in the range of 5 to 50 ° C, preferably 10 to 45 ° C, more preferably 15 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably about 20 to 240 seconds.

  A drying process is normally performed by drying at 20-70 degreeC, Preferably it is 25-60 degreeC for 3 to 5 minutes.

  Furthermore, iodine ion treatment can be performed in the drying step. For the iodine ion treatment, for example, an aqueous solution containing iodine ions with potassium iodide or the like is used. The potassium iodide concentration is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. In the iodine ion impregnation treatment, the temperature of the aqueous solution is usually about 15 to 60 ° C, preferably 25 to 40 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds.

  The stage of iodine ion treatment is not particularly limited as long as it is before the drying process. Uniaxial stretching process. It can also be performed simultaneously with the metal ion treatment and boric acid treatment. It can also be carried out after washing with water.

  In this way, a polarizer comprising a polyvinyl alcohol film that is dyed with at least a dichroic dye and contains metal ions is obtained. The obtained polarizer can be made into a polarizing plate provided with a transparent protective layer on at least one surface thereof according to a conventional method. It can be provided as a coating layer made of a transparent protective layer polymer or as a laminate layer of a film. As the transparent polymer or film material for forming the transparent protective film, an appropriate transparent material can be used, but a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property and the like is preferably used. Examples of the material for forming the transparent protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile, Examples thereof include styrene polymers such as styrene copolymers (AS resins), polycarbonate polymers, and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. The transparent protective film can also be formed as a cured layer of thermosetting or ultraviolet curable resin such as acrylic, urethane, acrylurethane, epoxy, and silicone.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  Moreover, it is preferable that a protective film has as little color as possible. Therefore, Rth = [(nx + ny) / 2−nz] · d (where nx and ny are the main refractive index in the plane of the film, nz is the refractive index in the film thickness direction, and d is the film thickness). A protective film having a retardation value in the film thickness direction of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  As the protective film, a cellulose polymer such as triacetyl cellulose is preferable from the viewpoints of polarization characteristics and durability. A triacetyl cellulose film is particularly preferable. On the other hand, a protective film such as triacetylcellulose has a large retardation value Rth in the thickness direction and has a problem of coloring, but contains an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the resin composition to be used, those having a thickness direction retardation value Rth of 30 nm or less can be used, and coloring can be almost eliminated. In addition, when providing a protective film in the both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used.

  The surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusing layer, antiglare layer and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

  An adhesive is used for the adhesion treatment between the polarizer and the transparent protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and water-based polyesters. The said adhesive agent is normally used as an adhesive agent which consists of aqueous solution, and contains 0.5 to 60 weight% of solid content normally.

  The polarizing plate of the present invention is produced by bonding the transparent protective film and the polarizer using the adhesive. The adhesive may be applied to either the transparent protective film or the polarizer, or to both. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. Bonding of a polarizer and a transparent protective film can be performed with a roll laminator or the like. The thickness of the adhesive layer is not particularly limited, but is usually about 0.1 to 5 μm.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. The transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it, and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by transparent the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And an alignment film of a liquid crystal polymer, and a liquid crystal polymer alignment layer supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of the liquid crystal layer, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, a retardation film, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things, such as a thing, can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of the liquid crystal display device and the like can be improved. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a long mirror alkyl type, fluorine type or molybdenum sulfide, can be used.

  In the present invention, the polarizer, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as an adhesive layer include, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, and a cyanoacrylate. It may be a compound having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a compound based on nickel or a nickel complex salt compound.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  The present invention will be specifically described below with reference to examples and comparative examples. In addition,% in each example is weight%.

Example 1
A 80 μm-thick polyvinyl alcohol film (average polymerization degree 2400, saponification degree 99.9%) was uniaxially wet-stretched up to 3 times, and then iodine having a potassium iodide concentration of 0.3% and an iodine concentration of 0.04% Dyeing was performed by immersing in an aqueous solution at 30 ° C. for 50 seconds. Next, wet stretching was performed at 60 ° C. while dipping in an aqueous solution having a boric acid concentration of 4% and a zinc sulfate concentration of 6% for 75 seconds to a total stretching ratio of 6 times. Next, the film was immersed in pure water at 25 ° C. for 10 seconds for washing, and then dried at 50 ° C. for 4 minutes to obtain a polarizer.

Example 2
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution having a boric acid concentration of 4% and a cobalt sulfate concentration of 6%. It was.

Example 3
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution of boric acid concentration of 4% and nickel sulfate concentration of 6%. It was.

Comparative Example 1
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution having a boric acid concentration of 4% and a zinc chloride concentration of 6%. It was.

Comparative Example 2
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution having a boric acid concentration of 4% and a cobalt chloride concentration of 6%. It was.

Comparative Example 3
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution having a boric acid concentration of 4% and a nickel chloride concentration of 6%. It was.

Comparative Example 4
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution having a boric acid concentration of 4% and a zinc acetate concentration of 6%. It was.

Comparative Example 5
A polarizer was obtained in the same manner as in Example 1 except that the aqueous solution having a boric acid concentration of 4% and the zinc sulfate concentration of 6% was changed to an aqueous solution having a boric acid concentration of 4% and a zinc nitrate concentration of 6%. It was.

(Evaluation)
The metal content and the retention rate of the polyvinyl alcohol film (polarizer) before and after the washing treatment with pure water in the above Examples and Comparative Examples were measured. Moreover, the sulfur atom content in the polarizer finally obtained after washing treatment and drying was measured. The results are shown in Table 1. The metal content and sulfur content were measured by FP method using fluorescent X-ray ZSX manufactured by Rigaku Corporation. Moreover, the presence or absence of the stain | pollution | contamination on the surface of the polarizer after water washing was evaluated visually according to the following criteria. ○: No appearance stains. X: White powder adhered.

実施例では、硫酸金属塩を用いており、金属の保持率が高く、水洗浄に用いる水洗浴中の金属イオンを低濃度に保持しやすく、金属イオンによる偏光子表面の汚染を防止できる。一方、比較例では金属の保持率が低く、金属イオンによる偏光子表面の汚染を防止ができない。

In the examples, metal sulfate is used, the metal retention rate is high, the metal ions in the water washing bath used for water washing can be easily kept at a low concentration, and contamination of the polarizer surface by metal ions can be prevented. On the other hand, in the comparative example, the metal retention rate is low, and contamination of the polarizer surface with metal ions cannot be prevented.

Claims (8)

In the manufacturing method of a polarizer including a step of performing a water washing step and then a drying step after subjecting the polyvinyl alcohol film to at least a dyeing treatment step with a dichroic dye, a uniaxial stretching treatment step and a metal ion treatment step.
A method for producing a polarizer, characterized in that a metal sulfate is used in the metal ion treatment step.   The polyvinyl alcohol film is subjected to at least a dyeing treatment step with a dichroic dye, a uniaxial stretching treatment step, a metal ion treatment step and a boric acid treatment step, followed by a water washing step and then a drying step. Item 2. A method for producing a polarizer according to Item 1.   3. The production of a polarizer according to claim 2, wherein the polyvinyl alcohol film is subjected to a dyeing treatment step with a dichroic dye, and then a uniaxial stretching treatment step, a metal ion treatment step, and a boric acid treatment step. Method.   The polarizer obtained by the manufacturing method in any one of Claims 1-3.   The polarizer according to claim 4, comprising a sulfur atom.   The polarizing plate which provided the transparent protective layer in the at least single side | surface of the polarizer of Claim 4 or 5.   An optical film, wherein at least one polarizing plate according to claim 6 is laminated. An image display device comprising the polarizing plate according to claim 6 or the optical film according to claim 7.